(Meth)acrylic acid (The term (meth)acrylic acid in this description implies “acrylic acid or methacrylic acid”.) or esters thereof are easily polymerizable compounds, and are compounds which form an explosive composition at around ordinary temperature, usually from 0 to 50° C. It is therefore necessary to keep the oxygen concentration in the gas-phase part in the production apparatus or storage apparatus for such compounds at a value within a given range. Namely, oxygen concentrations in the ambient gas lower than the given range result in the occurrence of polymerization reaction, while oxygen concentrations therein higher than the range result in the formation of an explosive composition.
An object of the invention is to provide a method of supplying an ambient gas by which an ambient gas having a given composition can be stably supplied to a production apparatus or storage apparatus for a compound necessitating strict ambient gas regulation during the production, storage, or handling thereof, such as (meth)acrylic acid or an ester thereof which are easily polymerizable and form an explosive composition at ordinary temperature, in a manner not influenced by fluctuations in the amount of the gas used.